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AS CHEMISTRY > GROUP 2 > Flashcards

GROUP 2 Flashcards

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1
Q

Describe the trend in atomic radius in group 2

A

Increases down the group

More shells of electrons

Bigger atom

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2
Q

Describe the trend in melting point of group 2

A

Decreases down the group

Metallic binding weakens
As atomic size increases

Distance between positive ions and delocalised ions increases

Electrostatic forces weaken

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3
Q

Describe the trend in 1st ionisation energy of group 2

A

Increases down group

Outermost electrons held more weakly
Further from nucleus

Outer shell more shielded

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4
Q

Describe the trend in reactivity in group 2

A

Increases down the group

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5
Q

How do the group 2 elements react with oxygen

A

Burn

Mg burns a bright white flame (MgO white solid with high melting point due to ionic bonding)

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6
Q

How does Mg react with oxygen without a flame

A

Magnesium oxide forms on the outside of Mg ribbons

Must be cleaned by emery paper

Gives false result

Because Mg and MgO react at different rates

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7
Q

How do the group 2 elements react with cold water

A

Form hydroxides and hydrogen

X(OH)2 (aq) + H2

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8
Q

How does magnesium react with steam and warm water

A

Burns in steam to produce MgO and hydrogen (bright white flame)

Slower reaction in warm water
Produces magnesium hydroxide and hydrogen

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9
Q

Outline the observations made when group two elements react with water

A

Fizzing (more vigorous down group)

Metal dissolving (faster down group)

Solution heating up (more down group)

CALCIUM ONLY: White precipitate forms

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10
Q

Why is titanium a useful metal?

A

Abundant

Low density

Corrosion resistant

Used to make strong light alloys

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11
Q

Why can’t titanium be extracted with carbon or electrolysis

A

TiC (titanium carbide) forms rather than titanium

Titanium has to be very pure

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12
Q

Outline the steps in which titanium is extracted

A

TiO2 + 2Cl2 > TiCl4 + 2CO (at 900C)

TiCl4 is purified by fractional distillation in Ar atmosphere

TiCl4 + 2Mg > Ti + 2MgCl2 (Ar atmosphere at 500C)

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13
Q

Why is titanium expensive

A

Mg is expensive

Batch processes (slower process requiring more labour and energy lost when reactor is cooked)

Argon atmosphere and need for moisture removal

High temperatures

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14
Q

Describe the trend in solubility in down group 2 hydroxides

A

Increases down the group

Appear as white precipitates when insoluble

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15
Q

Describe the state of magnesium hydroxide in water

A

Insoluble

Slightly alkaline so hydroxide ions must be produced

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16
Q

Outline the simplest ionic equation for the formation of Mg(OH)2 (s)

A

Mg2+ (aq) + 2OH- (aq) > Mg(OH)2 (s)

17
Q

How is magnesium hydroxide used in industry

A

Medicine to neutralise excess acid in the stomach and treat constipation

Mg(OH)2 + 2HCl > MgCl2 + 2H2O

Safe due to weak alkaline state

18
Q

Describe the reaction of calcium hydroxide with water

A

Reasonably soluble

19
Q

Outline the uses of calcium hydroxide in industry

A

Neutralise acidic soil

Test for CO2

Limewater turns clear to cloudy

Due to CaCO3 production

20
Q

Describe the solubility of barium hydroxide

A

Easily dissolves

Strongly alkaline

21
Q

Describe the trend in solubility of group 2 sulphates

A

Decreases down the group (less soluble)

BaSO4 least soluble

22
Q

Outline the full and ionic equations for the formation of the precipitate with group 2 sulphates

A

SrCl2(aq) + Na2SO4(aq) > 2NaCl(aq) + SrSO4(s)

Sr2+(aq) + SO4^2-(aq) > SrSO4(s)

23
Q

Outline the use of BaSO4 in industry

A

Absorbs x-Rays

To show up the gut on an x-Ray image

safe due to low solubility

24
Q

How does barium metal react with sulphuric acid

A

Slowly

Insoluble barium sulphate produces covers the surface if metal to act as a barrier to further attack

Ba + H2SO4 > BaSO4 + H2

25
Q

How is BaCl2 solution acidified with hydrochloride acid used as a reagent to test for sulphate ions

A

Ba2+(aq) + SO4^2-(aq) > BaSO4(s)

Barium sulphate is a white precipitate

Other anions give a negative result

26
Q

Why is hydrochloric acid used to test for the presence of a sulphate ion

A

To react with carbonate impurities found in salts

That would frozen barium carbonate a white participate

That gives a false result

27
Q

How can insoluble salts be formed?

A

Mixing appropriate ion solutions so a precipitate is formed

28
Q

What is a spectator ion

A

An ion not changing state

And not chasing oxidisation number

29
Q

What are the steps to writing an ionic equations for a precipitation reaction

A

Full equation
Ba(NO3)2(aq) + Na2SO4(aq) > BaSO4(s) + 2NaNO3(aq)

Separate (aq) solutions into ions
Ba2+ + 2NO3- + 2Na+ + SO4^2- > BaSO4 + 2Na+ + 2NO3-

Cancel out spectator ions
Ba2+ + SO4^2+ > BaSO4

AS CHEMISTRY (17 decks)

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